The present invention relates to an oil separator that separates oil contained in blow-by gas of an engine.
Conventionally, blow-by gas returning devices are known that return blow-by gas, which leaks out from combustion chambers of an engine to a crankcase, to an intake passage, thereby ventilating the crankcase. Blow-by gas contains oil mist. When the oil mist collects on the inner surface of the intake passage, foreign matter contained in intake air adheres to the oil mist, which may cause formation of deposit. Accordingly, oil separators have been proposed that separates and recovers oil mist in blow-by gas. For example, an oil separator disclosed in Japanese Laid-Open Patent Publication No. 9-88544 blows blow-by gas that has flowed into the oil separator through an inlet port on a plurality of diverting plates located in a blow-by gas passage, thereby recovering oil mist on the diverting plates through a drain port. On the other hand, the oil separator allows the blow-by gas, from which oil mist has been separated, to flow from an outlet port to an intake passage.
In the oil separator of the above publication, oil mist on the diverting plates is guided to the drain port while the blow-by gas is diverted along a blow-by gas passage. Therefore, the direction along which the oil mist is guided and the direction along which the blow-by gas flows intersect with each other, which may splash the oil mist anew. Such repeated splashing of oil mist reduces the recovery rate of oil mist. As a result, blow-by gas containing a considerable amount of oil mist is returned to the intake passage.